During a constant tracer infusion, the dilution of the infused tracer yields a measure of that molecule’s rate of appearance.  One can measure the turnover of numerous molecules using this strategy. One can determine the kinetics glucose, glycerol and protein using [6,6-²H₂]glucose, [²H₅]glycerol and [²H₅]phenylalanine.

This test requires a catheterized animal.